Re: Print expected tokens in yyerror function.

[Hans Aberg]

On 29 Mar 2008, at 13:22, Claudio Saavedra wrote:
> > The problem is that after an error token has arrived in the input,
> > additional reductions can take place before an error is issued by the
> > parser. So, although errors are detected, they are issued at a point
> > hampering good error recovery.
>
> That's exactly what the deferred parsing mechanism takes care of.  
> If an
> implementation, with a deferral level of k tokens, detects an error at
> certain point, the state of the parser is restored to the state it was
> before the last k tokens were shifted, "undoing" as well the
> corresponding reductions. Then, the error diagnosis and correction
> mechanism is invoked.

Then it might be usable (but see below).

> [If I'm moving OT, please say]

The feature most asked for is finding the correct set of lookahead  
token, to be used in an interactive parser. The error recovery thing  
seems to be rather out of vogue these days, in view of very  
interactive computer programming - it is fairly easy to fix the  
problems and recompile. It is still important to have good error  
messages, of course, identifying the point where the error occurred.

> I recommend reading 2.1.3 and 2.3.1 from [BF87], where this is  
> explained
> in complete detail.
...
> [BF87] http://portal.acm.org/citation.cfm?id=22719.22720

It seems to be a member thing. :-)

  Hans Aberg